The present invention relates to a device for iontophoresis to be applied through skin or mucous, and in particular, relates to a device for iontophoresis for administering appropriate quantity of drug at respective spotted regions to be treated.
Iontophoresis is percutaneous absorption enhancing system using electricity as external stimulation, and its principle is that barrier penetration through skin by drug molecules is enhanced mainly by energization, that is, based on a force to move positively charged molecules from a positive electrode to a negative electrode and to move negatively charged molecules from the negative electrode to the positive electrode, in an electric field generated between the positive electrode and a negative electrode. (Refer to Journal of Controlled Release, Vol. 18, 1992, pp. 213-220; Advanced Drug Delivery Review, Vol. 9, 1992, p. 119; Pharmaceutical Research, Vol. 3, 1986, pp. 318-326)
A conventional iontophoresis device has such a problem that quantity of dosage is different and skin is irritated due to individual difference in impedance in the region to be applied , but in recent years, a constant current apparatus is used so that a predetermined level of current is maintained despite of such a difference in impedance.
The constant current apparatus, which takes it advantage that delivery speed of a drug and current quantity are correlated, is capable of maintaining drug delivery speed at a constant, not based on impedance due to individual difference. In addition, since as for skin irritation an approximate current density not more than 0.2 mA/cm2 is considered to be low-irritating in general, the current quantity (formulation areaxc3x97maximum current densityxe2x89xa7predetermined current quantity) to be obtained from an area of formulation (an electrode structure) applied to skin and a maximum current density, being set at not more than 0.2 mA/cm2 serves to give rise to an effect that safetiness is maintained.
However, when an applicable area covers a wide range, currents do not always flow in an homogeneous fashion based on status of locations to be treated, in the above described constant current apparatus, either, and in some cases, heterogeneity in current may be occurred. In such cases, sufficient drug dosage is not implemented at a part of the region to be treated, and moreover, overdosage of a drug takes place at the other part of the region to be treated, in a result, high current density could cause inconveniences such as skin burning, etc.
As a device to dissolve these problems, Japanese Patent Laid-Open No. 61-100264 specification, for example, discloses an applicator having means for supplying constant current to a plurality of drug containing means and respective containers, and in addition, National Publication of International Patent Application No. 7-507951 specification discloses a device including a current-Miller circuit comprising a plurality of electrode segments each of which contains a constant-current source, and a circuit thereof. The prior art divides an applicable region into a plurality of parts and supplies an equal current to each divided applicable region so that dispersion of current density at the applicable region is made to be a minimum.
However, the prior art discloses nothing about supplying the spotted regions to be treated with proper currents (that is, drugs) simultaneously in case of local treatment for which iontophoresis device may be frequently used. For example, by using a handling-convenient device in the case where there exist spotted regions suffering from herpes zaster and urticaria, etc., each region to be treated could be supplied with a proper current (that is, drug) at the same time, and thus its resulting therapeutic efficiency is expected to be remarkably improved, but such a device is conventionally not yet known.
It is, therefore, an object of the present invention to provide a handling-convenient device for iontophoresis which can supply a proper quantity of current each spotted region suffering from disease at the same time.
The present inventors have been earnestly and repeatedly exerting themselves on researches to attain the object, and consequently, have enabled various spotted regions to be treated to have a desired quantity of drug dosage by connecting a plurality of connecting cords with respective output terminals of a power source apparatus having a plurality of current control circuits supplying predetermined currents, and thereby, have found out that drugs can be dosed at a high bioavailability through skin with good repeatability, and reached the present invention.
The device for iontophoresis according to the present invention comprises a power source apparatus having a plurality of output terminals outputting currents of the predetermined values adjusted by a plurality of current control circuits, respectively, and a plurality of connecting cords, each cord being connected with one of the output terminals of the power source apparatus at one end thereof and being connected with an electrode structure at the other end. Here one end of a connecting cord may be formed in an attachable/detachable fashion with output terminals of the power source apparatus. This way, connecting cords can be connected in accordance with a number of applicable portions of the electrode structures, and unnecessary connecting cords can be detached.
In addition, another device for iontophoresis according to the present invention comprises a power source apparatus having a plurality of output terminals outputting currents of the predetermined values adjusted by a plurality of current control circuits, respectively, and a connecting cord portion having a base coupled to the power source apparatus in an attachable/detachable fashion, a plurality of input terminals disposed on the base corresponding to each of the output terminals of the power source apparatus and a plurality of connecting cords, each cord being connected with one of the output terminals of the power source apparatus at one end thereof and being connected with an electrode structure at the other end. Thus, the power source apparatus and connecting cord parts are mutually made attachable/detachable so that one of those parts can be replaced based on the necessity. In addition, one end of a connecting cord may be formed to be attachable/detachable with the input terminals on the base.
The power source apparatus may includes a voltage adjusting circuit to adjust an output voltage in accordance with an output current value. Such an arrangement can serve to keep the output voltage at a voltage which is required and minimum value to maintain a constant current. In addition, with the power source apparatus itself being adjusted, or with connection relationships among connecting cords, the electrode structure, and the output terminals of the power source apparatus being altered, predetermined current values of respective electrode structures can be made variable in accordance with a plurality of regions suffering from diseases and area suffering from diseases. Moreover, the other ends of the connecting cords are formed so as to be attachable/detachable with the electrode structure.
With the configuration described above, a handling-convenient device for iontophoresis can be obtained which can supply a good quantity of current for each spotted portion suffering from disease, at the same time is available.